Yes, ask Haruka more questions

You ask Haruka whether she felt turned off by the fact that both of you are mother and son, and basically committing incest. The answer that you got was quite brutally honest. Despite carrying you for nine months, your mother barely spent any time with you growing up, and to her, apart from sharing some DNAs, you're just like another person who she didn't know.

"Aren't you afraid that you'll get pregnant?" you asked.

"When I saw you last night, I knew that we'll ended up having sex. As for your question, isn't pregnancy is an expected outcome of sexual intercourse? We derive so much pleasure and gratification from the act that we accept its natural outcome."

From Haruka's reply, you arrived to two conclusions. One, she didn't mind getting pregnant, viewing it as a logical conclusion of sex. Two, despite her alluring body, she has yet to give birth to ten babies. That meant, she wasn't promiscuous as you thought.

Knowing that it wouldn't do to keep things as it were, you had to make a decision on the way forward of your relationship with her.